1. Field of the Invention
This invention relates to post-mix beverage dispensers, such as for soft drinks and juices, and in particular to an inexpensive, positive displacement metering pump therefor useful with a pressurized source of concentrate.
2. Description of the Prior Art
Positive displacement, metering (portioning), pumps with check valves are known for use in post-mix beverage dispensers for juice wherein the juice concentrate is not under pressure. One such pump includes a double acting water pump connected to and driving a double acting concentrate pump. The water pressure operates the pump, and the pump chambers have the desired volume ratio of concentrate to water to perform the volumetric ratio control or metering of the two liquids. However, such a pump can not be used with a pressurized source of concentrate, because the check valves will allow "blow-thru," which is concentrate flowing directly through the pump, in effect, bypassing the pump and thus bypassing the volumetric ratio control performed by the pump.
A known way to eliminate flow through the check valves when a pressurized reservoir is employed requires placing a spring loaded poppet valve in the concentrate outlet. Force closing the poppet would have to be set at some value greater than the maximum inlet pressure. If the closing force was less than the maximum inlet pressure and a higher pressure was countered, non-metered flow would occur. The disadvantage of this known scheme is that the poppet would also be required to pressurize the concentrate to a value greater than the closing force of the pump. Operating the pump at higher pressure would greatly decrease the life of the pump components. A primary object of the present invention is to maintain a back pressure that is just slightly greater than the inlet pressure.
Regarding the post-mix beverage dispensing system of the present invention it is known to convert a pressurized juice dispensing system not using a metering pump to one using a positive displacement pump, however, in such known conversion it is necessary to go to the expense, time and trouble of converting the pressurized concentrate source to a vented source so that the concentrate will not be under pressure.
It is an object of the present invention to overcome the above-mentioned problems in the prior art, so that such a positive displacement, metering pump with check valves can also be used with a pressurized source of concentrate, without requiring an unacceptably large, heavy and expensive pump.
It is another object of this invention to provide a post-mix beverage dispenser positive displacement, concentrate metering pump provided with check valves, with means for preventing "blow-thru" of concentrate from a pressurized source.
It is another object of the invention to convert a pressurized juice dispensing system not using a metering pump to one using a positive displacement pump, without the necessity and expense of converting the pressurized concentrate source to a vented source.
It is another object of this invention to prevent "blow-thru" of concentrate in a post-mix beverage dispensing system using a positive displacement metering pump by pressurizing the outlet line with the pressure of the inlet line plus an additional pressure, rather than just pressurizing the outlet line to a set pressure, which would require the pump to have to overcome an unnecessarily high outlet pressure.
It is another object of this invention to provide a post-mix soft drink dispensing system including a pressurized concentrate source and a positive displacement concentrate metering pump using check valves, that includes means for pressurizing the outlet line therefrom to the pressure of the inlet line plus an additional pressure sufficient to prevent the "blow-thru" of pressurized concentrate through the check valves of said pump.
It is a still further object of this invention to provide a post-mix beverage dispenser using a positive displacement, metering pump having check valves and means for pressuring the outlet line therefrom with the pressurized fluid used to pressurize the concentrate.
It is another object of the present invention to provide a post-mix beverage dispenser system including a positive displacement metering pump having check valves and means for pressurizing the outline line therefrom with the pressure of either the inlet line plus an additional pressure, or to the pressure of the pressurized fluid used to pressurize the concentrate, in combination with a pressurized source of concentrate including a pressurizable canister connected to the concentrate line, means for holding and dispensing a quantity of pliable juice concentrate at a temperature below 32.degree. F., means for pressurizing the canister, and means for heating concentrate in the concentrate line between the canister and the pump.